When we started developing terashare we initially wanted to use the technology that is also used by reep.io (webrtc). We however decided against it because webrtc is currently not supported in Internet Explorer. Also, we designed terashare to be used for large files, and with webrtc you need to keep the browser tab open during the entire download and you need to copy to the entire file in the local storage of the browser before you can make another copy to for example your Downloads folder (ok for smaller files, not ok when you are sending a 500GB file).

Last but not least, in Belgium a lot of people are behind a NAT-router, and the NAT holepunching in webrtc often does not work very well in our experience.

It's a technology with a lot of potential though!